add(bDiv);  bDiv.addActionListener(new PressBDiv()); 
	      add(bSqrt);  bSqrt.addActionListener(new PressBSqrt()); 
	      add(bInt);  bInt.addActionListener(new PressBInt()); 
	      add(bMul);  bMul.addActionListener(new PressBMul()); 
	      add(bSin);  bSin.addActionListener(new PressBSin()); 
	      add(bBack);  bBack.addActionListener(new PressBBack()); 
	      add(bSub);  bSub.addActionListener(new PressBSub()); 
	      add(bCos);  bCos.addActionListener(new PressBCos()); 
	      add(bCE);  bCE.addActionListener(new PressBCE()); 
	      add(bAdd);  bAdd.addActionListener(new PressBAdd()); 
	      add(bYx);  bYx.addActionListener(new PressBYx()); 
	      add(bEqual);  bEqual.addActionListener(new PressBEqual()); //注册监听器以监听事件源产生的事件